1. Field of the Invention
The invention generally relates to access control techniques, and more particularly, to methods for access control with a back-off timer for low priority devices or Machine Type Communication (MTC) devices, and apparatuses using the same.
2. Description of the Related Art
For a long time, various machines have been provided to make our lives more convenient in every way. Generally, machines, nowadays, are equipped with computing processors and software to accommodate us with more intelligence-based services. With the advancement of wireless communications, Machine Type Communication (MTC) has been developed to enable communications between remote machines for exchanging information and operating without human interaction. Especially for critical public infrastructures, such as water treatment facilities or bridges, MTC sensors may be employed to monitor the operation statuses of facilities and report measurement results back to control centers via wireless communication networks, such as the Global System for Mobile communications (GSM) technology, General Packet Radio Service (GPRS) technology, Enhanced Data rates for Global Evolution (EDGE) technology, Wideband Code Division Multiple Access (WCDMA) technology, Code Division Multiple Access 2000 (CDMA-2000) technology, Time Division-Synchronous Code Division Multiple Access (TD-SCDMA) technology, Worldwide Interoperability for Microwave Access (WiMAX) technology, Long Term Evolution (LTE) technology, LTE-Advanced technology, and others.
Take the LTE technology in compliance with the 3GPP TS 23.060 specification, v10.1.0 (referred to herein as the TS 23.060 specification) and the 3GPP TS 24.008 specification, v10.1.0 (referred to herein as the 24.008 specification) as an example. A low priority indicator or MTC indicator is defined for indicating that a Mobile Station (MS) is tolerant to delays. An ME may be configured for MTC during manufacturing, and/or when accessing the service network, by Open Mobile Alliance (OMA) Device Management (DM) and/or Subscriber Identity Module/Universal Subscriber Identity Module (SIM/USIM) Over-The-Air (OTA). For an MS configured for MTC or configured as a low priority device, a back-off timer, T3245, is started with a random value in the range from 24 hrs to 48 hrs, when a PLMN identity is added to the “forbidden PLMN list” or the “forbidden PLMN for GPRS service” list, or when the SIM/USIM is set as invalid for GPRS or non-GPRS services. The situation may occur when the service network associated with the PLMN identity is congested or overloaded and wishes to decrease the communication traffic. Once the back-off timer is started, the MS is forbidden to access the service network associated with the PLMN identity until the back-off timer expires, and when the back-off timer expires, the MS erases the “forbidden PLMN list” and the “forbidden PLMN for GPRS service” list and sets the SIM/USIM as valid for GPRS or non-GPRS services, so that it may access the service network associated with the PLMN identity again.